The object of this proposal is to continue investigating the effects of an electrical field on epiphyseal plate growth in order to determine the eventual feasibilty of using electrical stimulation in the treatment of shortened extremities in children. The proposed investigation is designed: (1) to determine the parameters of voltage and current required to produce maximum epiphyseal plate growth as measured by macrophotography, H3-thymidine, Ca45, and S35 incorporation, and metaphyseal tetracycline labeling in in vitro and in vivo models, (2) to determine the morphologic effects of electric fields on the growth plate by quantitating changes in cytoplasmic components by means of point-counting analysis of electron micrographs and by quantitating the surface charge of chondrocyte cell membranes using a colloidal iron hydroxide stain visualized at the ultrastructural level, and (3) to determine Ca45 release from isolated growth plate chondrocytes, and calcium uptake, uptake capacity, and release from isolated growth plate mitochondria, in various oxygen tensions and electrical fields.